Unsaturated hydrocarbons by oxidative dehydrogenation over ferrite catalyst



United States Patent UNSATURATED HYDROCARBONS BY OXIDATIVE DEHYDRQGENATIQN OVER FERRITE CAT- ALYT lLaimonis llsajars, Princeton, and Louis J. Croce, East Brunswick, NJ, assignors to Petra-Tex Chemical Corporation, Houston, Tex., a corporation of Delaware No Drawing. Filed .ian. 2, 1964, Ser. No. 335,343

8 Claims. (Cl. 260-680) This invention relates to a process of dehydrogenating organic compounds at elevated temperatures in the presence of oxygen, halogen and particular catalysts. The catalysts of this invention comprise those selected from the group consisting of strontium ferrite and barium ferrite.

Strontium ferrite and barium ferrite are known commercial products which are useful, for example, in the formation of coatings suitable for high temperature applications. One method for the formation of these ferrites is by the reaction under certain conditions of iron carbonate or iron hydroxide with a carbonate of the desired metal other than iron in the presence of an atmosphere containing oxygen and a catalyst for the formation of the ferrite.

Hydrocarbons to be dehydrogenated according tothe process of this invention are hydrocarbons of 4 to 7 carbon atoms and preferably are hydrocarbons selected from the group consisting of saturated hydrocarbons, monoolefins, diolefins and mixtures thereof of 4 to 5 or 6 carbon atoms having a straight chain of at least four carbon atoms and cycloaliphatics. Examples of preferred feed materials are butene-l, cis-butene-2, trans-butene-Z, 2-methylbutene-1, 2-methylbutene-2, Z-methylbutene-B, n-butane, butadiene-1,3, methyl butane, cyclohexane, cyclohexene, Z-methylpentene-l, 2-methylpentene-2 and mixtures thereof. For example, n-butane may be converted to a mixture of butene-l and butene-2 or may be converted to a mixture of butene-l, butene-2 and/ or butadiene-l,3. A mixture of n-butane and butene-2 may be converted to butadiene-1,3 or to a mixture of butadiene-l,3 together with some butene-Z and butene-l. Vinyl acetylene may be present as a product, particularly when butadiene-l,3 is used as a feedstock. Thus, the process of this invention is useful in converting hydrocarbons to less saturated hydrocarbons of the same number of carbon atoms. The major proportion of the hydrocarbon converted will be to less saturated hydrocarbons of the same number of carbon atoms. Particularly the preferred products are butadiene-l,3 and isoprene. Useful feeds may be mixed hydrocarbon streams such as refinery streams, or the olefin containing hydrocarbon mixture obtained as the product from the dehydrogenation of hydrocarbons. In the production of gasoline from higher hydrocarbons by either thermal or catalytic cracking a hydrocarbon stream containing predominantly hydrocarbons of 4 carbon atoms may be produced and may comprise a mixture of butenes together with butadiene, butane, isobutane, isobutylene and other ingredients in minor amounts. These and other refinery byproducts which contain normal, ethylenically unsaturated hydrocarbons are useful as starting materials. Although various mixtures of hydrocarbons are useful, the preferred hydrocarbon feed contains at least 50 weight percent of a hydrocarbon selected from the group consisting of butene-l, butene-2, n-butane, butadiene-1,3, 2- methylbutene-l, Z-methylbutene-2, 2-methylbutene-3 and mixtures thereof, and more preferably contains at least 70 weight percent, of one or more of these hydrocarbons (with both of these percentages being based on the total weight of the organic composition of the feed to the reactor). Any remainder may be, for example, essen- Patented Feb.

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tially aliphatic hydrocarbons. This invention is particularly useful to provide a process whereby the major product of the hydrocarbon converted is a dehydrogenated hydrocarbon product having the same number of carbon atoms as the hydrocarbon fed.

It is one of the advantages of this invention that halogen may also be added to the reaction gases to give excellent results. The addition of halogen to the feed is particularly effective when the hydrocarbon to be dehydrogenated is saturated. The halogen fed to the dehydrogenation zone may be either elemental halogen or any compound of halogen which would liberate halogen under the conditions of reaction. Suitable sources of halogen are such as hydrogen iodide, hydrogen bromide and hydrogen chloride; aliphatic halides such as ethyl iodide, methyl bromide, 1,2-dibromo ethane, ethyl bromide, amyl bromide and allyl bromide; cycloaliphatic halides such as cyclohexylbromide; aromatic halides such as benzyl bromide; halohydrins such as ethylene bromohydrin; halogen substituted aliphatic acids such as bromoacetic acid; ammonium iodide; ammonium bromide; ammonium chloride; organic amine halide salts such as methyl amine hydrobromide; and the like. Mixtures of various sources of halogen may be used. The preferred sources of halogen are iodine, bromine and chlorine and compounds thereof such as hydrogen bromine, hydrogen iodide, hydrogen chloride, ammonium bromide, ammonium iodide, ammonium chloride, alkyl halides of one to six carbon atoms and mixtures thereof, with the iodine and bromine compounds being particularly preferred, and the best results having been obtained with ammonium iodide, bromide or chloride. When terms such as halogen liberating materials or halogen materials are used in the specification and claims, this includes any source of halogen such as elemental halogens, hydrogen halides or ammonium halides. The amount of halogen, calculated as elemental halogen, may be as little as about 0.0001 or less mol of halogen per mol of the hydrocarbon compound to be dehydrogenated to as high as 0.2 or 0.5. The preferred range is from about 0.001 to 0.09 mol of halogen per mol of the hydrocarbon to be dehydrogenated.

Oxygen will be present in the reaction zone in an amount within the range of 0.2 to 2.5 mols of oxygen per mol of hydrocarbon to be dehydrogenated. Generally, better results may be obtained if the oxygen concentration is maintained between about 0.25 and about 1.6 mols of oxygen per mol of hydrocarbon to be dehydrogenated, such as between 0.35 and 1.2 mols of oxygen. The oxygen may be fed to the reactor as pure oxygen, as air, as oxygen-enriched air, oxygen mixed with diluents and so forth. Based on the total gaseous mixture entering the reactor, the oxygen ordinarily will be present in an amount from about 0.5 to 25 volume percent of the total gaseous mixture, and more usually will be present in an amount from about 1 to 15 volume percent of the total. The total amount of oxygen utilized may be introduced into the gaseous mixture entering the catalytic zone or sometimes it has been found desirable to add the oxygen in increments, such as to different sections of the reactor. The above described proportions of oxygen employed are based on the total amount of oxygen used. The oxygen may be added directly to the reactor or it may be premixed, for example with a diluent or steam.

The temperature for the dehydrogenation reaction will be greater than 250 C., such as greater than about 300 C. or 375 C., and the maximum temperature in the reactor may be about 650 C. or 750 C. or perhaps higher under certain circumstances. However, excellent results are obtained within the range of or about 300 C. to 575 C. such as from or about 325 to or about 525 C. The

temperatures are measured at the maximum temperature in the reactor. An advantage of this invention is that lower temperatures of dehydrogenation may be utilized than are possible in conventional dehydrogenation processes. Another advantage is that large quantities of heat do not have to be added to the reaction as was previously required.

The dehydrogenation reaction may 'be carried out at atmospheric pressure, superatmospheric pressure or at sub-atmospheric pressure. The total pressure of the system will normally be about or in excess of atmospheric pressure, although sub-atmospheric pressure may also desirably be used. Generally, the total pressure will be between about 4 p.s.i.a. and about 100 or 125 p.s.i.a. Preferably the total pressure will be less than about 75 p.s.i.a. and excellent results are obtained at about atmospheric pressure.

The initial partial pressure of the hydrocarbon to be dehydrogenated will be equivalent to less than one-half atmosphere at a total pressure of one atmosphere. Generally the combined partial pressure of the hydrocarbon to be dehydrogenated together with the oxygen will also be equivalent to less than one-half atmosphere at a total pressure of one atmosphere. Preferably, the initial partial pressure of the hydrocarbon to be dehydrogenated will be equivalent to no greater than one-third atmosphere or no greater than one-fifth atmosphere at a total pressure of one atmosphere. Also, preferably, the initial partial pressure of the combined hydrocarbon to be dehydrogenated plus the oxygen will be equivalent to no greater than one-third or no greater than one-fifth atmosphere at a total pressure of one atmosphere. Reference to the initial partial pressure of the hydrocarbon to be dehydrogenated means the partial pressure of the hydrocarbon as it first contacts the catalytic particles. An equivalent partial pressure at a total pressure of one atmosphere means that one atmosphere total pressure is a reference point and does not imply that the total pressure of the reaction must be operated at atmospheric pressure. For example, in a mixture of one mol of butene, three mols of steam, and one mol of oxygen under a total pressure of one atmosphere, the butene would have an absolute pressure of one-fifth of the total pressure, or roughly six inches of mercury absolute pressure. Equivalent to this six inches of mercury butene absolute pressure at atmospheric pressure would be butene mixed with oxygen under a vacuum such that the partial pressure of the butene is 6 inches of mercury absolute. The combination of a diluent such as nitrogen, together with the use of a vacuum may be utilized to achieve the desired partial pressure of the hydrocarbon. For the purpose of this invention, also equivalent to the six inches of mercury butene absolute pressure at atmospheric pressure would be the same mixture of one mol of butene, three mols of steam and one mol of oxygen under a total pressure greater than atmospheric, for example, a total pressure of 20 p.s.i.a Thus, when the total pressure in the reaction zone is greater than one atmosphere, the absolute values for the pressure of the hydrocarbon to be dehydrogenated will be increased in direct proportion to the increase in total pressure above one atmosphere.

The partial pressures described above may be maintained by the use of diluents such as nitrogen, helium or other gases. Conveniently, the oxygen may be added as air with the nitrogen acting as a diluent for the system. Mixtures of diluents may be employed. Volatile compounds which are not dehydrogenated or which are dehydrogenated only to a limited extent may be present as diluents.

Preferably the reaction mixture contains a quantity of steam, with the range generally being between about 2 and 40 mols of steam per mol of hydrocarbon to be dehydrogenated. Preferably steam will be present in an amount from about 3 to 35 mols per mol of hydrocarbon .4 to be dehydrogenated and excellent results have been obtained within the range of about 5 to about 30 mols of steam per mol of hydrocarbon to be dehydrogenated. The functions of the steam are several-fold, and the steam does not merely act as a diluent. Diluents generally may be used in the same quantities as specified for the steam. Excellent results are obtained when the gaseous composition fed to the reactor consists essentially of hydrocarbons, inert diluents and oxygen as the sole oxidizing agent.

The gaseous reactants may be conducted through the reaction chamber at a fairly wide range of flow rates. The optimum flow rate will be dependent upon such variables as the temperature of reaction, pressure, particle size, and whether a fluid bed or fixed bed reactor is utilized. Desirable flow rates may be established by one skilled in the art. Generally, the flow rates will be within the range of about 0.10 to 25 liquid volumes of the hydrocarbon to be dehydrogenated per volume of reactor containing catalyst per hour (referred to as LHSV), wherein the volumes of hydrocarbon are calculated at standard conditions of 25 C. and 760 mm. of mercury. Usually, the LHSV will be between 0.15 and about 5 or 10. For calculation, the volume of reactor containing catalyst is that volume of reactor space excluding the volume displaced by the catalyst. For example, if a reactor has a particular volume of cubic feet of void space, when that void space is filled with catalyst particles, the original void space is the volume of reactor containing catalyst for the purpose of calculating the flow rate. The gaseous hourly space velocity (GHSV) is the volume of the hydrocarbon to be dehydrogenated in the form of vapor calculated under standard conditions of 25 C. and 760 mm. of mercury per volume of reactor space containing catalyst per hour. Generally, the GHSV will be between about 25 and 6400, and excellent results have been obtained between about 38 and 3800'. Suitable contact times are, for example, from about 0.001 or higher to about 5 or 10 seconds, with particularly good results being obtained between 0.01 and 3 seconds. The contact time is the calculated dwell time of the reaction mixture in the reaction zone, assuming the mols of product mixture are equivalent to the mols of feed mixture. For the purpose of calculation of residence times, the reaction zone is the portion of the reactor containing catalyst.

The catalytic surface described is the surface which is exposed in the dehydrogenation zone to the reactor, that is, if a catalyst carrier is used, the composition described as a catalyst refers to the composition of the surface and not to the total composition of the surface coating plus carrier. Catalyst binding agents or fillers may be used, but these will not ordinarily exceed about 50 percent or 60 percent by weight of the catalytic surface. These binding agents and fillers will preferably be essentially inert. The catalyst will by definition be present in a catalytic amount. Generally the ferrite selected from the group consisting of strontium ferrite and barium ferrite together with any iron and the atoms selected from the group consisting of strontium and barium not combined as the ferrite will be the main active constituents. The amount of catalyst will ordinarily be present in an amount greater than 10 square feet of catalyst surface per cubic foot of reaction zone containing catalyst. Of course, the amount of catalyst may be much greater, particularly when irregular surface catalysts are used. When the catalyst is in the form of particles, either supported or unsupported, the amount of catalyst surface may be expressed in terms of the surface area per unit weight of any particular volume of catalyst particles. The ratio of catalytic surface to weight will be dependent upon various factors, including the particle size, particle size distribution, apparent bulk density of the particles, amount of active catalyst coated on the carrier, density of the carrier, and so forth. Typical values for the surface to weight ratio are such as about one-half to 200 square meters per gram, although higher and lower values may be used.

The dehydrogenation reactor may be of the fixed bed or fluid bed type. Conventional reactors for the production of unsaturated hydrocarbons are satisfactory. Excellent results have been obtained by packing the reactor with catalyst particles as the method of introducing the catalytic surface. The catalytic surface may be introduced as such or it may be deposited on a carrier by methods known in the art such as by preparing an aqueous solution or dispersion of a catalytic material and mixing the carrier with the solution or dispersion until the active ingredients are coated on the carrier. If a carrier is utilized, very useful carriers are silicon carbide, pumice and the like. When carriers are used, the amount of catalyst on the carrier will generally be between about 5 to 75 weight percent of the total weight of the active catalytic material plus carrier. Another method for introducing the required surface is to utilize as a reactor a small diameter tube wherein the tube wall is catalytic or is coated with catalytic material. Other methods may be utilized to introduce the catalytic surface such as by the use of rods, wires, mesh, or shreds and the like of catalytic material.

According to this invention, the catalyst is autoregenerative and the process is continuous. Moreover, small amounts of tars and polymers are formed as compared to some prior art processes.

The catalysts are not limited to those illustrated in the examples. Other methods of preparation and other compositions may be employed. Valuable catalysts were produced comprising as the main active constituents in the catalytic surface exposed to the reaction gases, iron, oxygen and an element from the group consisting of strontium and barium. The best results are obtained with catalysts having iron as the predominant metal in the catalytic surface. Preferably at least about 55 and generally at least about 70 weight percent of the atoms of iron and the second metal will be present as the ferrite. Included in the definition of ferrite are the active intermediate oxides. The preferred ferrites are the ferrites having a hexagonal crystal structure. Suitable catalysts will contain from or about 9 to 15 atoms of iron per atom of strontium or barium, and preferably will have about 12 atoms of iron. It has been found that superior results may be obtained with catalysts having a defect crystal structure. The desired catalysts may be obtained by conducting the reaction to form the ferrite at relatively low temperatures, that is, at temperatures lower than some of the very high temperatures used for the formation of ferrites prepared for semiconductor applications. Generally the temperature of reaction for the formation of the catalysts comprising the particular ferrites will be less than 1300 C. and preferably less than 1150 C. The reaction time at the elevated temperature in the formation of the catalyst may preferably be from about 5 minutes to 4 hours at elevated temperatures high enough to cause formation of the ferrite but less than about 1150 C. Any iron not present in the form of the ferrite will desirably be present predominantly as gamma iron oxide. The alpha iron oxide will preferably be present in an amount of no greater than 40 weight percent of the catalytic surface, such as no greater than about 30 weight percent.

Some improvement in catalytic activity may be obtained by reducing the catalyst of the invention. The reduction of the catalyst may be accomplished prior to the initial dehydrogenation, or the catalyst may be reduced after the catalyst has been used. It has been found that a used catalyst may be regenerated by reduction and, thus, even longer catalyst life obtained. The reduction may be accomplished with any effective reducing gas which is capable of reducing iron to a lower valence such as hydrogen, carbon monoxide or hydrocarbons. Generally the flow of oxygen will be stopped during the reduction step. The temperature of reduction may be varied but the process is most economical at temperatures of at least about 6 200 C., with the upper limit being about 75 C. or 900 C. or even higher under certain conditions.

In the following examples will be found specific embodiments of the invention and details employed in the practice of the invention. Percent conversion refers to the mols of hydrocarbon consumed per 10 mols of hydrocarbon fed to the reactor, percent selectivity refers to the mols of product formed per mols of hydrocarbon consumed, and percent yield refers to the mols of product formed per mol of hydrocarbon fed.

Example 1 Barium ferrite (Columbian Carbon Co. EG-4, lot 101, 261) was used as the catalyst. The barium ferrite had about 12 atoms of iron per atom of barium. The barium ferrite was coated on 4 to 8 mesh fused alumina pellets in an amount of roughly 30 percent by weight barium ferrite based on the total weight. n-Butane was dehydrogenated at atmospheric pressure in a Vycor glass reactor (36" x 1 OD.) having a 50 cc. catalyst bed supported on a 1 deep layer of A" x A" OD. Vycor Raschig rings. n-Butane, oxygen and steam and HBr were introduced into an adapter located on top of the glass reactor, and the eflluent gases were passed through a cold-water condenser to remove most of the steam. Sample of the effluent gases were withdrawn with a syringe at the exit from the condenser. They were analyzed in a vapor chromatograph. The n-butane used was 0?. grade, 99.0 mol percent minimum; the oxygen was commercial grade, purity 99.5 plus, and steam was generated from the distilled water.

The mixture of n-butane, oxygen, HBr and steam was fed to the reactor in an amount of 1.25 mols of oxygen, 20 mols of steam and 0.08 mol of bromine per mol of nbutane (calculated as Br The LHSV was 0.2. At a maximum temperature in the reactor of 510 C. butadiene 1,3 was obtained at a yield of 72 mol percent.

Example 2 Example 1 was repeated with the exception that the barium ferrite was obtained from Stackpole Carbon Company (Ceramagnet BG-KB 2976). The barium ferrite had a barium content equivalent to 13.8 percent calculated as BaO. At a reactor temperature of 520 C., the yield of butadiene was 67 percent.

Example 3 The catalyst and reactor of Example 1 were used for this example. n-Butane was dehydrogenated to a mixture of butenes and butadiene. Oxygen was fed in an amount of 1.25 mols, helium was fed in an amount of 20 mols, and chlorine was fed in an amount of 0.3 mol (calculated as C1 but fed as HCl), all based on the mols of n-butane fed. The flow rate was 0.2 LHSV. At a reactor temperature of 550 C., the combined yield of butenes and butadiene was 60 percent.

Example 4 Butene-2 was dehydrogenated to butadiene, utilizing the barium ferrite catalyst of Example 1. 0.8 mol of oxygen, 20 mols of helium, and 0.03 mol of Br were fed per mol of butene-2. The flow rate was 0.6 LHSV. At a reactor temperature of 525 C., the yield of butadiene was 93 percent.

Example 5 The barium ferrite of Example 1 was used to catalyze the dehydrogenation of butene-2 to butadiene. No carrier was employed and the barium ferrite was slurried in water, dried, and broken into 4 to 8 mesh lumps which were used as a catalyst. The same reactor was used as in Ex ample l. The molar ratio of oxygen to butene-2 was 0.75 and 30 mols of steam were utilized per mol of butene-2. The LHSV was 1. The butene was dehydrogenated to butadiene at a reactor temperature of 450 C.

7 Example 6 A strontium ferrite catalyst was formed as follows: 80.0 grams of strontium chloride and 48.7 grams of ferric chloride were dissolved in 350 cc. of distilled water. A second solution was prepared by dissolving 100 grams of potassium hydroxide in 750 cc. of distilled water. A reddish brown slurry was obtained by adding the mixed chloride solution into the potassium hydroxide solution with stirring. The slurry was then dewatered by filtering and the coprecipitate was washed with distilled water until it was neutral. The mixture was dried in an oven at a temperature of 130 C. After drying, the black solid was reacted at 900 C. to form the strontium ferrite. The strontium ferrite was a magnetic black solid. Example 1 was repeated with the strontium ferrite being substituted for the barium ferrite. A high yield of butadiene was obtained.

We claim:

1. A process for the dehydrogenation of hydrocarbons having at least four carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 250 C. a mixture of the said hydrocarbon to be dehydrogenated, halogen and from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium ferrite and barium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon.

2. A process for the dehydrogenation of hydrocarbons selected from the group consisting of n-butene, n-butane and mixtures thereof which comprises contacting in the vapor phase at a temperature of greater than about 325 C. a mixture of the said hydrocarbon to be hydrogenated, halogen and from about 0.25 to about 1.6 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium and barium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere.

3. A process for the dehydrogenation of hydrocarbons having at least four carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 325 C. a mixture of the said hydrocarbon to be dehydrogenated, from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon, halogen and from 2 to 40 mols of steam per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium ferrite and barium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon.

4. A process for the dehydrogenation of hydrocarbons having from 4 to 5 carbon atoms which comprises contacting in the vapor phase at a temperature of at least about 375 C. a mixture of the said hydrocarbon to be dehydrogenated, from 0.35 to 1.2 mols of oxygen per mol of the said hydrocarbon and less than 0.2 mol of halogen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium ferrite and barium ferrite wherein the atoms of iron are present in an amount of 55 to 89 weight percent based on the total weight of the atoms of iron and the element selected from the group consisting of strontium and barium, to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than onethird atmosphere at a total pressure of one atmosphere.

5. A process for the dehydrogenation of a hydrocarbon selected from the group consisting of n-butene, n-butane and mixtures thereof which comprises contacting in the vapor phase at a temperature of from 375 C. to 525 C. and at a pressure of 4 p.s.i.a. to 125 p.s.i.a. a mixture of the said hydrocarbon to be dehydrogenated, from about 0.25 to about 1.6 mols of oxygen per mol of the said hydrocarbon and less than 0.2 mol of bromine per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium ferrite and barium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-fifth atmosphere at a total pressure of one atmosphere.

6. A process for the dehydrogenation of butene to butadiene-1,3 which comprises contacting in the vapor phase at a temperature of from 375 C. to 575 C. and at a total pressure of less than p.s.i.a. a mixture of the said butene, from 8 to about 35 mols of steam, from 0.35 to 1.2 mols of oxygen per mol of the said butene and from .0001 to .09 mol of a halogen selected from the group consisting of iodine, bromine, chlorine and mixtures thereof per mol of said butene with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium ferrite and barium ferrite wherein the atoms of iron are present in an amount of 55 to 89 weight percent based on the total weight of the atoms of iron and the element selected from the group consisting of strontium and barium to produce butadiene-1,3.

7. A process for the vapor phase dehydrogenation of a hydrocarbon selected from the group consisting of n-butane, butene-1, butene-2 and mixtures thereof which comprises contacting in the vapor phase at a temperature of greater than 325 C. a mixture of the said hydrocarbon to be dehydrogenated, from 0.25 to 1.6 mols of oxygen per mol of the said hydrocarbon and from 0.0001 to .09 mol of bromine per mol of said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium ferrite and barium ferrite wherein the atoms of iron are present in an amount of about 55 to 89 weight percent based on the total weight of the atoms of iron and the element selected from the group consisting of strontium and barium to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-third atmosphere at a total pressure of one atmosphere.

8. A process for the dehydrogenation of aliphatic hydrocarbons having at least four carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 250 C. a mixture of the said hydrocarbon to be dehydrogenated, halogen and from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of strontium ferrite and barium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere, said catalyst having been reduced with a reducing gas.

References Cited by the Examiner UNITED STATES PATENTS 3,168,587 2/1965 Michaels et a1 260-6833 3,179,707 4/1965 Lee 260-669 3,207,811 9/1965 Bajars 260----680 DELBERT E. GANTZ, Primary Examiner.-

G. E. SCHMITKONS, Assistant Examiner.

UNITED STATES PATENT OFFICE Certificate Patent No. 3,303,234 Patented February 7, 1967 Laiinonis Bajars and Louis J. Croce Application having been made by Laimonis Bajars and Louis J. Croce, the inventors named in the patent above identified, and Pctro-Tex Chemical Corporation, Houston, Texas, a corporation of Delaware, the assignee, for the issuance of a certificate under the provisions of Title 35, Section 256, of the United States Code, adding the name of Maigonis Gabliks as a joint inventor, and a showing and proof of facts satisfying the requirements of the said section having been submitted, it 18 this 1st day of December 1970, certified that the name of the said Maigonis Gabliks is hereby added to the said patent as a joint inventor with the said Laimonis Bajars and Louis J. Croce.

FRED W. SHERLING Associate Solicitor. 

1. A PROCESS FOR THE DEHYDROGENATION OF HYDROCARBONS HAVING AT LEAST FOUR CARBON ATOMS WHICH COMPRISES CONTACTING IN THE VAPOR PHASE AT A TEMPERATURE OF GREATER THNA 250*C. A MIXTURE OF THE SAID HYDROCARBON TO BE DEHYDROGENATED, HALOGEN AND FROM 0.2 TO 2.5 MOLS OF OXYGEN PER MOL OF THE SAID HYDROCARBONS WITH A CATALYST FOR THE DEHYDROGENATION COMPRISING A FERRITE SELECTED FROM THE GROUP CONSISTING OF STRONTIUM FERRITE AND BARIUM FERRITE TO PRODUCE A DEHYDROGENATED HYDROCARBON PRODUCT HAVING THE SAME NUMBER OF CARBON ATMS AS THE SAID HYDROCARBON. 